19.5HP Briggs & Stratton - Yardman Mower Engine Problems

I have a handed down Yardman Lawn Tractor with a 19.5HP Briggs & Stratton 3672CN engine. Got this last year and ran fine all year without problems starting or running. Haven't run it in several months and when I tried it last week the battery was too low to turn engine over. Replaced battery but then engine would just crank and crank and never fire. Pulled air cleaner off and sprayed some starter fluid in and would run until fluid ran out and then cut off. Pulled carb and cleaned everything I could with carb cleaner and made sure everything was free moving. Pulled cap lock screws out and float was trapped under mid-gasket and didn't have a new gasket so I sprayed in the float area with carb cleaner without removing it. Pulled the plug on the side of the float area and let the carb cleaner run completely thru. Replaced fuel filter even though fuel was free flowing. Replaced carb and after starting with starter fluid a few time, it started running on it's own. Idled fast and stayed running smooth as long as I just let it sit there.
I put it in gear and moved forward and backwards a few times and as soon as any additional load was put on the engine, the engine would slow, the lower butterfly below the carb would start to shut and the engine would just cut off. Also, if I even just barely started to engage the blades the engine would die. Was told there was also an oil level safety on this engine but the oil level is correct. It appears that the engine runs fine but has no power under load. When any load is added to the idle condition the engine dies. I tried adjusting the metering needle screw on the carb but that had no effect unless I went in too far and then the engine would sputter and die.
Any and all help would be greatly appreciated as with the recent rains I will soon need a field guide to find my front door :O)
Scott snipped-for-privacy@gmail.com
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On Fri, 15 Jun 2007 06:24:13 -0700, infiniteMPG wrote:

Still got carb problems.
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The carb is pretty simple, the only thing I didn't dig into was the float. When the top cap is removed the gasket is stuck to the bottom of the carb housing. The float mechanism seems mounted to something in the top half and something is under the gasket in the bottom half. So unless I scrap the gasket off and replace it I can't seperate the halves. Does this sound like float issues? Should the entire float mechanism be relaced or could it just be sticking?
Sounds like a trip to the parts shop to get a gasket and a float or a complete rebuild kit. I checked and did not see ANY numbers or identifiers on the carb anywhere. How do you ask for a rebuild kit or float or would there just be one carb available on the 19.5hp 3672CN engine?
Thanks, Scott
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On Fri, 15 Jun 2007 14:18:31 +0000, infiniteMPG wrote:

It could go by the make and serial number of the mower but you could take the carb with you also. Sounds like the engine is dying because it's starving for fuel (unless it makes black smoke) when the governor pulls the throttle up and that could be a sign of low fuel level in the bowl (float/needle valve problem) You probably should call the parts department and ask the exactly what they need to look up a parts list for that carb.
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They wanted the stamped number off the engine block. I had the model of the mower but no help as it's old.

makes black smoke) when the governor pulls the throttle up and that could be a sign of low fuel level in the bowl (float/needle valve problem) You probably should call the parts department and ask the exactly what they need to look up a parts list for that carb.
I would of checked the float out better but didn't have the replacement gasket and the float is attached to the top part of the carb housing and some of it extends below the gasket so I couldn't remove it without scraping off the gasket. The local shop (and I trust these guys) is open tomorrow 8-1 so I am running by there. Good idea to bring the carb. Two bolts and it's in my hand. My Dad (who I got the mower from) just told me that he thinks it's carbon buildup in the heads and/or the exhaust system. I kind of doubt that as that would cause it to run bad all the time and not just when going under load. My hunch is pointing me towards the float as even when it starts to die if I spray starter fluid (or dribble some gas) directly in the carb it stays running until the fuel is used up. The float is not in a seperate "bowl" with a releif spring screw plug in the bottom like many small engines, it's in a machined out section of the bottom housing and only has one hex plug in the side and no drain in the bottom.
Thanks for the advice, I need it :O) Scott
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On Fri, 15 Jun 2007 20:41:34 +0000, infiniteMPG wrote:

makes black smoke) when the governor pulls the throttle up and that could be a sign of low fuel level in the bowl (float/needle valve problem) You probably should call the parts department and ask the exactly what they need to look up a parts list for that carb.

No problem. I was just trying to give a general description of a float and bowl and stuff. Make sure you get a new gasket for where the carb bolts on.
Now I'm headed out to fix the float on my 3850 watt generator powered by Tecumseh (or however it's spelled) The float is stuck open and fuel pours out the overflow tube :)
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wrote:

I agree it is not a carbon build-up on the head or piston. Pull the plug a look at the piston at top dead center, if you think it's necessary.
The spray makes it run, because it is starving for fuel as mentioned earlier.
The float and it's operation; would be my focus, for the moment.
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
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wrote:

If the gasket is seriously stuck - it needs to be replaced! You can make one with gasket material from the auto store. There may be a vacuum leak at the gasket.
The float neddle can be worn on the tip (rubber point) and needs to be checked to ensure the float works, Use a gauge to set the float...

Go to the B&S site, locate your model..they may sell the kit. Check for a local B&S service center.

Sticky/worn float needle is a great place to look. So far the OP has not gotten into the float parts, unless I missed it :-( - -- Oren
"The voices in my head may not be real, but they have some good ideas!"
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Update 6/16.2007 - Pulled a little 'stunt' last evening trying to get the model off the engine. Was told several places to look and ended up pulling all the side panels and hood off the mower and the side covers. When I was about to pull the top cover off I happened to look and there is a tag on the top of the top cover right in my face. Sometimes the most obvious is the hardest to notice.... duh!
MODEL - 42E777 / TYPE - 1280 01 / CODE - 9509215A
Ran down to a local mower shop this morning and got a complete carb rebuild kit for $13. Alos grabbed a new air filter and foam filter cover. Didn't know what I was doing totally and no instructions so I set off to do my best.
Pulled everything apart, got the float out, cleaned all the ports, replaced all the parts I could (one jet housing I couldn't get out and didn't want to damage so I cleaned as good as I could). Replaced the float, the springs, gaskets, seals, everything I could. Put everything back together, mounted it up and hoped for the best.
Sprayed a little starter fluid in and fired her up. Started right up, settled to idle quick and then I tried engaging the blades to put a load on the engine and it purred great! Put the filter on, restarted it and mowed. Nice feeling.
Was running a little s-l-o-w at full throttle so I think I have to adjust the settings a little but managed to mow a good portion of the yard before the sun baked my brain. Appears there are a couple adjustments on the carb, a needle screw under the bowl section of the float (which I beleive adjusts the mix), a screw on the throttle lever which I think only adjusts the idle speed, and a screw on the front of the engine that looks to be part of the throttle cable setting. Any help to increase the full throttle speed (I may of turned something when trying to fix it before)?
Thanks again for your assistance, Scott
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wrote:

Odd, there were no instructions. My last kit had the instructions and the float gauge....

It does feel good; especially when extra parts are left in the kit box! :-)

Just my method, but I increase the RPM on the engine and adjust it by "ear" At a higher RPM I can "tune" it.
Make small turns 1/8 to 1/4 turns on the screw.

-- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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"ear" At a higher RPM I can "tune" it. Make small turns 1/8 to 1/4 turns on the screw.
On which screw? There were three, one by the float (I think mix), one on the side of the carb (I think just low idle speed), and one down on the front of the engine that the throttle linkage runs thru. I guess I would assume that one?
Yeah, feels good and looks good. Was waiting for a letter from the neighborhood nazis.... errr, I mean the homeowner's association folks :O) Oh yeah, didn't put this in as I didn't think it mattered much at the time but when I was remounting the carb a couple days ago I must of had something not seated right and when I cranked on the front carb mount bolt I heard a loud POP and when I disassembled it I found the front tab flange the carb mounts on broke off in the cast metal. I actually used J-B Weld and it's solid and works. Love that stuff! :O)
Thanks again, Scott
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wrote:

Mixture screw, then adjust the idle when she sounds good on the "ear tune"!

That POP is telling you something. We just have to listen. Better the flange than the bolt in the block.
I've never been able to adjust a carb with a broken bolt flange :-))

-- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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On Sat, 16 Jun 2007 10:41:15 -0700, infiniteMPG wrote:

Running speed is set by the governor and throttle position. Make sure you have that back together properly. Wish I could visualize the setup but I don't have anything here to look at. Did you mention you had something on a pdf file?
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Didn't see any way to add a PDF file to the messages so I uploaded it and this is the link :
http://www.infinitempg.com/carbimages.pdf
This shows the right and left side view of the carb on the front of the engine, air cleaner assembly completely removed. I tweaked around with the mixture screw yesterday (this is not shown in either picture, it's below the square gas inlet assembly on the front of the carb) and got it to smooth out. Then played with the idle adjustment screw (on the right side view right beside the breather hose hanging loose). I got it to idle fast and ride a lot better then before but not perfect. Still managed to mow the rest of my yard. The thing I noticed is that the throttle adjustment didn't do a thing for changing the engine speed, the only thing I could do is adjust the idle screw. The throttle cable is the cable you can see in the bottom of the left side view and there is an adjustment screw where it mounts to the front of the engine. This runs thru a linkage and ends up changing the plate stop that rests against the idle adjustment screw in the right side view. When I move the throttle adjustment it moves the linkage on the front of the engine but it barely causes any movement in the stop plate on the side of the carb. Not sure what's up with that as I used to be able to throttle it so slow with the adjustment before the engine would almost cut off.
So I still have some adjustment issues but now (hopefully) you can see the setup I have on the engine.

Me neither as I repaired the flange with JB Weld and it seems to be holding solid and true :O) That "POP" is a sound I'd rather not hear again :O)
Thanks, Scott
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Oh yeah, the place the throttle linkage connects into the system on the front of the engine looks like this :
http://www.infinitempg.com/carbadj.jpg
Didn't know if that would help but it shows the way this linkage cable ties in.
Thanks again, Scott
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wrote:

Are there any kinks, bends, or loose connections along this cable?
Is it difficult to move; meaning corrosion in the casing? Lube as mentioned to get the full range of motion.
-- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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wrote:

The throttle cable can be binding/or not adjusted.
From the end view of the throttle cable spray a lubricant inside the cable and hold the end up so the lube runs inside the cable casing.. move the cable back and forth to ensure it operates smoothly. Then attach it back to the carb and adjust the range of movement.
(Tortoise - Rabbit)

-- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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